The present invention relates to a recognizing method and apparatus of circular holes to be utilized, e.g., in a visual recognizing device for a screwing robot whereby each position of two circular overlapping holes is automatically recognized by processing images of the holes taken by a TV camera or the like.
The aforementioned type of device has been provided and widely employed lately as a visual recognizing device for a screwing robot.
FIG. 7 shows the constitution of a circular hole recognizing device used hitherto. Two circular holes formed in two members to be screwed together are picked up by a visual sensor 100 such as a TV camera or the like, and the obtained image signals are converted to digital values at an image input part 101. The image data after conversion is stored in an image memory 102. The image data in the image memory 102 is displayed at an image display part 103, and at the same time fed and processed at an image processing part 104 to recognize each position of the circular holes.
The image processing part 104 has, in order to process the image data as above, a hole area detecting means 105 for detecting an area of each circular hole and a gravity center detecting means 106 for detecting the center of gravity of the area of the circular hole detected by the detecting means 105. Referring to FIG. 8, the areas of the two circular overlapping holes (j) and (k) and the center of gravity (l) of the areas are automatically detected in the image processing part 104. Accordingly, 10 the robot is able to perform automatic screwing on the basis of the above-described recognition.
However, the two circular holes (j) and (k) are not always overlapped as perfectly as illustrated in Fig. 8. If the circular holes (j) and (k) partially overlap at an overlapping area (m) as shown in FIG. 9, the conventional device detects only the area of the upper circular hole (j), or the overlapping area (m) in some cases. The center of gravity of the upper circular hole (j) is not coincident with that of the lower circular hole (k). Also, even if the center of gravity (n) of the overlapping area (m) is detected, the center of gravity (n) does not correspond to that of any of the upper and lower circular holes (j) and (k).
As a result, the robot is unable to screw the members correctly if based on the above recognition of the center of gravity.